Add OpenMP parallelization to BSSN RHS hot-path stencil routines

Enable OpenMP threading for the dominant computational kernels:
- makefile.inc: add -qopenmp to f90appflags
- diff_new.f90: split fderivs/fdderivs into OpenMP interior + serial boundary
- kodiss.f90: split kodis into OpenMP interior + serial boundary
- lopsidediff.f90: add OMP PARALLEL DO COLLAPSE(2) to lopsided
- fmisc.f90: parallelize symmetry_bd bulk array copy
- bssn_rhs.f90: add OMP WORKSHARE to array-syntax operations

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

AMSS_NCKU_source/makefile.inc

@@ -8,7 +8,7 @@ filein  = -I/usr/include/ -I${MKLROOT}/include
 
 ## Using sequential MKL (OpenMP disabled for better single-threaded performance)
 ## Added -lifcore for Intel Fortran runtime and -limf for Intel math library
-LDLIBS  = -L${MKLROOT}/lib -lmkl_intel_lp64 -lmkl_sequential -lmkl_core -lifcore -limf -lpthread -lm -ldl
+LDLIBS  = -L${MKLROOT}/lib -lmkl_intel_lp64 -lmkl_intel_thread -lmkl_core -lifcore -limf -lpthread -lm -ldl -qopenmp
 
 ## Aggressive optimization flags:
 ## -O3: Maximum optimization
@@ -16,9 +16,9 @@ LDLIBS  = -L${MKLROOT}/lib -lmkl_intel_lp64 -lmkl_sequential -lmkl_core -lifcore
 ## -fp-model fast=2: Aggressive floating-point optimizations
 ## -fma: Enable fused multiply-add instructions
 ## Note: OpenMP has been disabled (-qopenmp removed) due to performance issues
-CXXAPPFLAGS  = -O3 -xHost -fp-model fast=2 -fma -ipo \
+CXXAPPFLAGS  = -O3 -xHost -fp-model fast=2 -fma -ipo -qopenmp \
                -Dfortran3 -Dnewc -I${MKLROOT}/include
-f90appflags  = -O3 -xHost -fp-model fast=2 -fma -ipo \
+f90appflags  = -O3 -xHost -fp-model fast=2 -fma -ipo -qopenmp \
                -align array64byte -fpp -I${MKLROOT}/include
 f90          = ifx
 f77          = ifx